I think I'm going to cheat with this one and just go for character traits or bookish things in romance books that make me swoon. I don't think I could think of 10 books that stand out that would fit the "swoon" category.

Confidence - I dig when the hero of the story is confident, on the side of domineering, but with respect. When he's assertive with wanting the heroine and not indecisive with his decisions.

Sense of Humor - Attractive men need attractive senses of humor. I like a book in romance where they both have humor, adds a lot of spice to the punch.

Sultry Appeal - I like the hero who has the sultry looks and the subtle moves when it comes to romancing the female in romance books.

A Way With Words - I like eloquent speech

Forced Relationships - These can add a lot to the spice of a romance story, such as where they have to work together

Jealousy - I don't like jealous men but it's fun in romance books where the heroine is in love with someone else (or thinks she is), but the hero is determined to win her heart and pursue her.

Mysterious - I like when the hero and heroine don't give everything away with their secrets and such and save something for the ending of the book.

Charming - With clothing, the way he carries himself, deals with children

Reading - Any heroine or hero who reads or the theme involves something with books is always a fun bonus.